The figure foretold in Bajoran prophecy who would find the Celestial Temple and speak for the Prophets, a role that Kai Opaka recognises in Benjamin Sisko in 2369.
The Emissary of the Prophets is a figure of Bajoran scripture, the one who will open the Celestial Temple and act as a link between the Prophets and their people. In the Deep Space Nine pilot Emissary, Kai Opaka identifies Benjamin Sisko as that person, and his discovery of the wormhole seems to confirm it.
Sisko is uneasy with the title for years. In Accession he gladly hands it to Akorem Laan, a poet who emerges from the wormhole after two centuries, only to take it back when Akorem tries to restore the caste system. From Rapture onwards he accepts the role and the visions that come with it.
The series later reveals that the Prophets arranged his birth. In What You Leave Behind he fulfils the role by stopping Dukat and Winn in the Fire Caves and joins the Prophets in the Celestial Temple.